#include<iostream>
using namespace std;
using ll=long long;

int main(){
	ll n,a,b;
	cin>>n>>a>>b;
	ll sum=(a-1)*(2*n-a+2)/2;
	ll tot=sum+b;
	int ch=(tot-1)%26;
	cout<<(char)('A'+ch)<<endl;
	return 0;
}	
